A computerized methodology for analyzing autoradiographic spot images associated with recombinant DNA bacterial colonies has been developed in collaboration with scientists in NCI. This system represents a unique refinement in a method to directly identify cloned sequences complementary to messenger RNA that are developmentally or hormonally induced. Spot density measurements are computed from digitized images produced via microdensitometry. These measurements are corrected for variability in exposure and local background, calibrated to hybridization standards, and normalized for comparison purposes. The system provides a variety of graphical and tabulation output that effectively summarizes experimental results and identifies significant induced hybridization events.